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Ladder Safety Calculator — 4:1 Ratio, Height & Footing Check
Check ladder setup safety: correct 4:1 angle (75 degrees), the 9m rest-platform rule, 1m handhold extension above the landing point, and footing type assessment — per HSE guidance.
Height to the landing or work point
Leaning ladders only — the ladder should extend ~1m (three rungs) above the landing for a handhold. Not applicable to stepladders.
At least 1m (three rungs) above the landing per HSE/LA455 — do not reduce below 1m
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How We Calculate This
This calculator checks ladder setup safety based on the 1-in-4 (4:1) angle rule, the landing handhold extension and footing condition, per HSE guidance and the Work at Height Regulations 2005. For leaning ladders (single-section and extension) it works out the base distance, ladder length and pitch angle; for A-frame stepladders it shows the stepladder-specific rules instead, since the angle and extension geometry do not apply to them.
Safety checks
- 1-in-4 ratio (leaning ladders): Base distance = height ÷ 4 (gives a 75° pitch)
- Handhold extension (leaning ladders): at least 1m (about three rungs) above the landing
- Height: there is no absolute maximum height for a ladder, but at/above 9m above the base a rest platform or landing area should be provided at suitable intervals
- Ladder length: √(height² + base²) from Pythagoras
- Stepladders: firm, level ground; do not stand and work on the top three steps (including a step forming the very top of the stepladder) unless there is a suitable handhold; light, short-duration work only
Frequently Asked Questions
The 4:1 rule means for every 4 metres of height, the base of the ladder should be 1 metre from the wall. This gives an angle of approximately 75° from the ground, which provides the best balance between stability and comfort. Too steep (over 80°) risks the ladder falling backwards; too shallow (under 70°) risks the feet sliding out.
HSE guidance is that a leaning ladder should extend at least 1 metre (about three rungs) above the landing point or roof edge to give a secure handhold for stepping on and off. Under the Work at Height Regulations 2005 you must provide a safe handhold unless an alternative is available. Never step off at the top rung, and do not work off the top three rungs. This handhold rule applies to leaning ladders only, not to A-frame stepladders.
HSE is clear that there is no maximum height for using a ladder. However, where a ladder rises 9 metres or more above its base, landing areas or rest platforms should be provided at suitable intervals. In practice, an extension ladder gives a realistic working reach up to around 15m and a single-section ladder much less; stepladders are for light, short-duration work (commonly up to about 4m). Ladders should only be used for short-duration work — typically up to 30 minutes in one position — and where the risk of injury from a fall is low. For longer tasks or higher access, a scaffold, tower or MEWP is usually the right choice well before 9m.
Per HSE and the Work at Height Regulations, do not use a ladder if: the work will take more than 30 minutes, you need both hands for the work, the weather is poor (high winds, rain, ice), the ground is uneven or soft, there is no way to secure the ladder, or you need to carry heavy/bulky items. Use a scaffold, tower, or MEWP instead.
Ladders must be prevented from slipping. Options in order of preference: (1) tie the top to a secure point, (2) tie the base (stiles, not rungs), (3) use a ladder stabiliser device, (4) have someone foot the ladder at the base. On soft ground, use a board under the feet. Never place a ladder on boxes, drums, or other unstable surfaces.
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Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.